Quenching solution for fluorescent photographic paper employed in the manufacture ofhalftone negatives



United States Patent QUENCHING SOLUTION .FOR FLUORESCENT PHOTOGRAPHIC PAPER EMPLOYED IN THE WACTURE 0F HALFTONE NEGA- Joseph E. Dulfy, and Joseph 'Sottysiak, Binghamton, N.Y., 'assignors, to General Aniline 8: Film Corporation, New York, N.Y., a corporation of Delaware No Drawing. Filed Nov. s, 1955, Ser. No. 544,813

l'Claim. or. 96-27) The present invention relates to quenching solutions for light sensitive photographic paper containing a fluorescent agent and employed as intermediate material for the preparation of halftonenegatives in the photo-engraving and photo-lithographic industry.

Procedures have been levised for producing halftone negatives in which an image is formed by freehand drawing, photography or the like, on a fluorescent-containing material, and the image thus prepared then photographed onto a light sensitive film or plate. A typical method of this kind is described in U.S. Patent 2,395,986, granted March 5, 1946. Where the intermediate print is produced on photographic fluorescent material, such material comprises a paper base containing either dispersed in it or in a separate layer at its surface a fluorescent dye and a light sensitive silver halide emulsion separated from the base by a water impermeable resinous barrier layer.

The fluorescent property of the base in such material is utilized by subsequently photographing the print thereon onto a film in ultraviolet light. This procedure increases the density of the shoulder area of the negative which corresponds to the high light area of the print without a corresponding increase in the portion of the negative corresponding to the denser areas of the print. This, in effect, is equivalent to a lengthening of the contrast scale thereby improving the balance and high light gradation of the resulting halftone separation negative.

The originals from which the intermediate prints are made in this process usually contain features which may be objectionable and require modification or elimination. Such art work, to improve quality, necessitates the employment of a quenching solution for the intermediate light sensitive paper which is capable of selectively dampening the fluorescence of the paper either by decreasing or entirely eliminating the fluorescence in certain areas of such paper, without changing the basic appearance in tungsten illumination of the print desired.

It has been proposed to eliminate the fluorescence of light sensitive photographic materials by the utilization of chemicals which react with the fluorescent dye to destroy its fluorescent power. It is to be emphasized, however, that this procedure is unsuitable where the emulsion is separated from the fluorescent material by means of a resinous barrier layer which acts to screen such chemicals from the fluorescent material.

It is, therefore, necessary to use a solution which effects dampening of the fluorescence in certain areas but not by a chemical reaction. Moreover, such a solution must also go smoothly on the photographic emulsion without salting out, i.e., without uneven deposition of the fluorescent dampening agent in the solution. The solution must also have suflicient adhesion to remain on the emulsion, once applied.

We have now found that a solution meeting these prerequisites is provided by an aqueous-organic solvent solution of a U.V. absorber and a small quantity of a spreading agent which prohibits salting out of the U.V. absorber. Such compositions and their use for decreas ing or eliminating the fluorescence in selected areas of intermediate light sensitive fluorescent paper for use in manufacturing halftone separation negatives, constitute the purposes and objects of the present invention.

The ultraviolet absorbing compounds contemplated for use herein must be capable of absorbing U.V. light without fluorescing. This eliminates the compounds generally used for the brightening of textiles, suchas, for instance, brightening agents derived from 4,4-diaminodiphenyl- 2,2-disulfonic acid or 4,4-diaminostilbene-2,2-disulfonic acid. Such compounds, because of their ability to fluoresce, would be incapable of dampening the fluorescence in the intermediate print paper.

The agents which are suitable are those which are sharply absorbent for U.V. light, such as 2,4-dihydroxybcnzophenone; 2,2-dihydroxy-4,4-dimethoxybenzophenone; 2,2'-4,4'-tetrahydroxybenzophenone, alone or in admixture with the dimethoxy derivative 4benzoylresorcinol; 2-phenylcinchoninic acid; 3-aminophenyl-8-hydroxycinchoninic acid and the xenylamines disclosed in application Serial 529,682, filed by Tulagin and Holistadt on August 22, 1955, and entitled Ultra-Violet Absorbing Compounds. Examples of this class of compounds are 4-amino-4-benzoylbiphenyl; 4-acetyl-4'-aminobiphenyl; 4-acetyl-4'-aminobiphenylphenylhydrazone and the like.

The U.V. absorbers are dissolved in a low boiling, neutral, liquid, water-miscible organic solvent, such as the alcohols, i.e., methanol, ethanol, propanol and the like; ketones such as methylethylketone, diethylketone and the like.

Once the particular U.V. absorber has been selected, it is no problem to determine a solvent having the above characteristics and which will be suitable for the intended use.

To expedite application of the solution to the emulsion, without salting out of the U.V. absorbent, we have found it necessary to employ a water soluble polyhydric alcohol having spreading properties. Polyhydric alcohols in this category are the polyalcohol amines, such as triethanolamine, diethanolamine and the like, glycerin, diethylene glycol and the like.

In making up the solutions, the U.V. absorbent is dissolved in the organic solvent, the required amount of spreading agent added and the solution diluted with water to the desired degree.

The following table illustrates the components and the parts by weight in which they may be employed in preparing the quenching solutions.

TABLE Parts by weight U.V. absorber .5-10 Organic solvent 15-50 Spreading agent 10-40 Water to make 500-1000 parts by weight.

The following examples, in which the parts are by weight, will serve to illustrate the invention, although it is to be understood that the invention is not limited thereto.

Example I One part of 2,4-dihydroxybenzophenone is dissolved in 25 parts of methanol and 22 /2 parts of triethanolamine are then added. The mixture is well stirred and distilled Water added to make a total of 500 parts. The solution is then filtered and ready for use.

Example II The composition is the same as in Example I, excepting that the U.V. absorber employed is a mixture of equal 3 parts of 2,2-dihydroxy-4,4'-dimethoxybenzophenone and 2,2'-4,4'-tetrahydroxybenzophenone.

Modifications of the invention will occur to persons skilled in the art and we, therefore, do not intend to be limited in the patent granted, except as necessitated by the appended claim.

We claim:

In a process of making halftone negatives from an original negative, which comprises printing the original negative on a light sensitive material containing a fluorescent dye dispersed in a paper base and photographing the resulting intermediate silver image print on a light sensitive photographic film, the improvement which comprises selectively dampening the fiuorescene in certain areas of the intermediate photographic print, without changing the appearance in tungsten illumination, by treating said selected areas with a solution containing a UN. absorber selected from the group consisting of 2,4-dihydroxybenzophenone, 2,2'-dihydroxy-4,4'-dimethoxybenzophenone and 2,2-4,4-tetrahydroxybenzophenone in a solvent mixture comprising water, a low boiling, water-miscible, neutral solvent selected from the group consisting of methanol, ethanol, propanol, I'neth- 4 ylethylketone and diethylketone, and a polyhydric alcohol spreading agent selected from the group consisting of triethanolamine, diethanolamine, glycerin, and diethylene glycol.

References Cited in the file of this patent V UIIITED STATES PATENTS 2,129,1 31 Hunter Sept. 6, 1938 OTHER REFERENCES The Merck Index, 6th ed., Merck 1952 972,:

under "lriethanolamine. e 

